Image guidance systems are becoming more common and widely adapted in neurosurgery. Such systems have been proven to increase the accuracy and reduce the invasiveness of a wide range of surgical procedures. Currently, image guided surgical systems (“Navigation Systems”) are based on obtaining a pre-operative series of imaging data, such as, e.g., MRI and CT which are registered to the patient in the physical world by means of an optical tracking system. Such optical tracking allows for detecting markers placed on a patient's skin (known as “fiducials”) and correlating them with their counterparts within such pre-operation imaging data.
In many conventional image guided operations, images generated from pre-operative scan data are displayed as two dimensional images in three orthogonal planes through the image volume, while a surgeon holds a probe that is tracked by a tracking system. When such a probe is introduced into a surgical field, the position of its tip is represented as an icon drawn on the images. By linking the preoperative imaging data with the actual surgical field, navigation systems can provide a surgeon (or other practitioner) with valuable information, i.e., the exact localization of a tool in relation to surrounding structures within the patient's body. This helps to relate the actual tissues of an intra-operative field to their images used in pre-operative planning.
However, in such systems the displayed images are only two dimensional, and to be fully utilized must be mentally reconciled into a three dimensional image in the surgeon's mind. Thus, sharing a problem which is common to all conventional navigation systems which present imaging data in 2D orthogonal slices, a surgeon has to make a significant mental effort to relate the spatial orientation of a pre-operative image series (displayed, for example, in separate axial, coronal, and sagittal planes) to the physical orientation of the patient's area of interest, such as, for example, a patient's head in a neurosurgical procedure which is often mostly covered by draping during the operative procedure. Other conventional systems display a three dimensional (“3D”) data set in a fourth display window. However, in such systems the displayed 3D view is merely a 3D rendering of pre-operative scan data and is not at all correlated to or merged with the surgeon's actual view of the surgical field. Thus, while using such systems, a surgeon is still forced to mentally reconcile the displayed 3D view with his real time view of the actual surgical field he or she is working in. This requires the cumbersome task of the surgeon continually switching his or her view between the 3D rendering of the object of interest (usually presented as an “abstract” object against a black background) and the actual surgical field. What is needed in the art is a less cumbersome method of presenting preoperative data to a surgeon during surgery so as to enhance his or her real time surgical navigation capabilities.